There is an optical link device to which a pair of optical fibers through which an optical signal is transmitted are connected and which transmits and receives data through the optical fibers.
Hereinbelow, an example of a conventional optical link device will be conceptually shown (see FIG. 7).
An optical link device a has an element mounting unit b and a lens body c disposed inside a not-shown housing.
The element mounting unit b has a light emitting element d and a light receiving element e respectively mounted thereon.
The lens body c comprises a transmission side lens unit f and a reception side lens unit g formed integrally.
A pair of optical fibers h, h are respectively connected to the housing of the optical link device a.
In a condition that the pair of optical fibers h, h are connected to the optical link device, when an electrical signal is inputted from an external device, for example, a personal computer, the electrical signal is photoelectrically converted in the light emitting element d and outputted from the light emitting element d to one of the optical fibers h as an optical signal (laser beam).
The optical signal outputted from the light emitting element d is inputted to the transmission side lens unit f of the lens body c, converged by the transmission side lens unit f and inputted to the other of the optical fibers h so that data transmission and reception is carried out.
On the other hand, when an optical signal is transmitted through the other of the optical fibers h, the transmitted optical signal is outputted from the optical fiber h toward the light receiving element e.
The optical signal outputted from the other optical fiber h is inputted to the reception side lens unit g of the lens body c and photoelectrically converted so that an electrical signal is generated. The electrical signal is inputted to the external device so that data transmission and reception is carried out.
However, in the conventional optical link device a, when the optical signal outputted from the light emitting element d is inputted to the lens body c, the optical signal may be possibly inputted from the transmission side lens unit f to the light receiving element e as a stray light owing to reflection and double refraction generated in the lens body c, as shown with an arrow P in FIG. 7, which may result in deterioration of the optical signal inputted from the optical fiber h to the light receiving element e.
In addition, the optical signal outputted from the light emitting element d toward the optical fiber h through the transmission side lens unit f may also reflect on a tip surface of the optical fiber h so that a stray light comes into the light receiving element e transmitting through the reception side lens unit g.
Therefore, in order to solve such problems, there is an optical link device 1 having a light shielding plate k provided between a transmission side lens i and a reception side lens j, which are separately formed (see FIG. 8).
In such an optical link device 1, the optical signal outputted from the light emitting element d to be a stray light is shielded by the light shielding plate k, and the stray light is prevented from coming into the light emitting element e.
However, in the optical link device 1, since a certain space for positioning the light shielding plate k is needed between the transmission side lens i and the reception side lens j, an interval between the lenses is required to be wide, which results in another problem that the optical link device becomes large.
Furthermore, because the transmission side lens i, the reception side lens j and the light shielding plate k are separately formed, there will be another problem that the number of parts required is increased and manufacturing cost will rise.
In view of this, the optical link device of the present invention has an object to avoid deterioration of a signal due to a stray light coming into a light receiving element and to have a device smaller in size.